Search results for "CVT"

Analysis of hybrid vehicle transmissions with any number of modes and planetary gearing: kinematics, power flows, mechanical power losses

2021

Abstract This paper is focused on upgrading a unified parametric model, available in the literature, that can perform both the analysis and the design of Power-Split Continuously Variable Transmissions (PS-CVTs), which are particularly promising to deploy in the hybrid electric powertrain. In particular, this work is focused on the analysis of PS-CVTs and proposes a new matrix approach for identifying the basic functional parameters underlying the model from the constructive layout of the transmission. This new method does not rely on a case-specific formulation, thus befits any power-split transmission, regardless of the number of planetary and ordinary gear sets and their constructive arr…

Direct analysis of power-split CVTs: A unified method

2018

Abstract This paper provides a fast kinematic analysis method for compound power-split CVTs, which consents to identify their functional parameters. Such parameters permit the assessment of power flows, torques and efficiency, and the design of equivalent transmissions by the use of a recently published mathematical model. The same method can easily address either simpler or more complex transmissions by mean of kinematic equivalent parameters, without the need to arrange separate systems of equations. As a case study, we performed the kinematic analysis of the “Voltec” multi-mode GM transmission.

Power losses in power-split CVTs: A fast black-box approximate method

2018

Abstract This paper addresses the mechanical losses of planetary transmissions, with particular attention to power-split CVTs in their hybrid electric versions. It provides unified layout-independent analytical relationships, which can be used for both analysis, design and control purposes, and a simplified approach; the latter overcomes the necessity to segment the operating range of the power-split CVT in order to keep its loss model physically consistent. An example of application to a real hybrid electric PS-CVT is performed to show the simplicity, accuracy and generality of the proposed method.

A simple method for the design of hybrid electric power-split cvts: A case study

2018

A brief parametric method for the preliminary design of hybrid electric Power-Split CVTs is performed. The desired torque-speed characteristic is obtained, and general control and optimization criteria are introduced in order to minimize the size of the required electric machines. The optimization is performed by mean of scheme-independent functional parameters, while a specific constructive design is proposed only later, along with possible full electric operations.

Approximate Closed-Form Solutions for the Shift Mechanics of Rubber Belt Variators

2009

The mechanical behavior of V-belt variators during the speed ratio shift is different from the steady operation as a gross radial motion of the belt is superimposed to the circumferential motion. The theoretical analysis involves equilibrium equations similar to the steady case, but requires a re-formulation of the mass conservation condition making use of the Reynolds transport theorem. The mathematical model of the belt-pulley coupling implies the repeated numerical solution of a strongly non-linear differential system. Nevertheless, an attentive observation of the numerical diagrams suggests simple and useful closed-form approximations for the four possible working modes of any pulley, o…

Analysis of the maximization of wind turbine energy yield using a continuously variable transmission system

2017

Abstract In this paper, an analytic study of the subject of mechanical power transmission in HAWT wind turbine has been carried out. For the most part, the study analyzes the use of continuously variable transmission (CVT) in order to allow the turbine and the electric generator to couple, allowing in turn, an unremitting transmission ratio adjustment. In low-wind sites, the design criteria suggest an oversizing of the wind turbine in order to generate adequate electrical power even at low wind speed. The proposed solution enhances the space of operating points since it allows the electric generator to release the rotational speed from the turbine one (limited due to structural integrity). …

Efficiency of Split-Way CVT's. A simplified model

2007

ABSTRACT In this paper, a general formula is obtained for the efficiency of all types of Split-Way CVT, consisting of one or two epicyclic trains, a number of fixed ratio gears and one variable speed unit (CVU). It is based on the application of the principle of virtual works and on the simplifying hypothesis that all the dissipation is lumped inside the CVU. The comparison with some experimental results from the literature shows a surprisingly good fit, also in the neighbourhoods of zero speed ratio. INTRODUCTION The possibility of changing the speed ratio continuously between the primary and the secondary shaft of a mechanical transmission is a very interesting topic, mainly in the automo…

The paradoxical management of service skills

2015

This paper focuses on service skills which are mobilized by front office agents when they are involved with customers. These skills are most of the time tacit. We consider that the way in which firms recognize these skills and contribute to their development is an important management issue. It is all the more important that a lot of jobs combine poor levels of qualification and highly situated skills.

Parametrical design of Split-Way CVTs

2016

La presente attività di ricerca si svolge presso l’Università degli Studi di Palermo nell’ambito di un corso di dottorato in Ingegneria dell’Innovazione Tecnologica, il quale si pone l’obiettivo di delineare una procedura semplice, generale e modulare per la progettazione, la modellistica ed il dimensionamento di trasmissioni meccaniche innovative, eventualmente coadiuvate da dispositivi di accumulo d’energia. In particolare, una crescente sensibilità verso le problematiche connesse all’efficienza energetica, e la conseguente ascesa dell’auto ibrida, ha fatto sì che negli ultimi anni le trasmissioni di tipo Split-way suscitassero, specie in virtù della loro capacità di consentire un certo s…

Split-Way CVTs: Parametric Analysis and Design

The thesis provides a parametric analytical method for the analysis and design of power-split continuously variable transmissions, which represent the state of the art for heavy-duty vehicles and hybrid electric cars. The functioning of any driveline is described by mean of a simple set of kinematic parameters, regardless of the constructive scheme. The calculation of the control torques remains straightforward even when both inertial effects and mechanical losses are taken into account. A simple design procedure is described and generalized in order to address any order of driveline, including multimode transmissions. The final layout is generated additively, without the need to analyze hu…